SPC AC 091301

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0801 AM CDT Tue Jun 09 2020

   Valid 091300Z - 101200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS
   SOUTHEAST NEBRASKA/NORTHEAST KANSAS...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE
   MIDWEST/OHIO VALLEY...

   ...SUMMARY...
   Scattered severe thunderstorms capable of large hail, damaging
   winds, and a few tornadoes are expected this afternoon and evening
   across parts of the central Plains and Missouri Valley. Other
   isolated severe storms including the possibility of a few tornadoes
   are expected across the Midwest and Ohio Valley.

   ...Central Plains/Missouri Valley...
   Have upgraded parts of the region for a focused severe risk that is
   anticipated to be maximized generally near the southeast
   Nebraska/northeast Kansas border vicinity this afternoon/early
   evening.

   A shortwave trough located along the Colorado/northern New Mexico
   Front Range this morning will continue eastward and reach eastern
   Kansas/southeast Nebraska by evening. Strong height falls will
   precede this upper trough, along with the exit region of a
   cyclonically curved mid/high-level jet, which will overspread a
   moderate to strongly unstable air mass ahead of an eastward-moving
   front/surface low. In particular, a surface low will develop
   east-northeastward across central/northeast Kansas this afternoon.
   Substantial surface heating ahead of the low and cold front should
   contribute to strong buoyancy arcing across eastern Kansas into
   southeast Nebraska, which will be just to the north of the surface
   low.

   Forecast soundings feature MLCAPE values in excess of 3000 J/kg
   across this region with minimal inhibition by early afternoon.
   Latest thinking is scattered supercells should first develop
   immediately east/northeast of the surface low, within the focused
   exit region of the 80kt+ mid-level jet. Convection is expected to
   initiate by around 19-20z and then spread east-northeastward along
   the Nebraska/Kansas border region. A few intense supercells can be
   expected. Wind profiles will be supportive of a tornado risk aside
   from very large hail. Storms may tend to cluster and become undercut
   by the advancing front during the early evening hours, but a large
   hail/damaging wind and some tornado threat will continue during the
   evening from far northeast Kansas/southeast Nebraska into southwest
   Iowa/northwest Missouri.

   ...Midwest/Lower Ohio Valley/Mid-South...
   A mid-level dry slot on the southern fringe of the Cristobal should
   continue to develop east-northeastward over southeast Missouri and
   western portions of Kentucky/Tennessee toward Illinois/Indiana
   through the afternoon. With a very moist air mass (low 70s F surface
   dewpoints) also developing northward, dry slot-related cloud breaks
   and diurnal heating will contribute to weakening inhibition and
   moderate buoyancy by afternoon, particularly across Illinois into
   western/central Indiana. The north/northeastward-expanding core of
   strongest low/mid-level winds will also reside within this same
   corridor, including an increasing mid-level westerly component this
   afternoon, which could boost the potential for somewhat longer
   duration/semi-discrete updraft rotation. A few tornadoes may occur
   across the region, along with isolated thunderstorm-related wind
   damage. Portions of Illinois (roughly the eastern half) into Indiana
   will be reevaluated in subsequent outlooks for a possible
   tornado-related risk upgrade (10% Enhanced). 

   Farther north, a transient supercell/brief tornado risk cannot be
   ruled out as far north as eastern Iowa/southeast Minnesota and
   western/southern Wisconsin this afternoon and early evening, and
   into Lower Michigan this evening.

   ...South Texas...
   A southeastward-moving cold front will overtake a pre-frontal
   dryline/surface trough later today. Strong surface heating, with
   temperatures warming to near 100F, near and ahead of the front will
   weaken the cap and a few high-based thunderstorms may develop by
   late afternoon. These storms would be capable of severe wind gusts
   and hail. Any such storms would likely persist and propagate
   southward tonight across Deep South Texas and the Rio Grande Valley
   with an isolated severe threat potentially continuing through the
   evening and possibly early in the overnight.

   ..Guyer/Leitman.. 06/09/2020

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